A display device incorporating a display panel configured to display an image and a touch panel adapted for touch sensing to detect user input provides a convenient user interface.
Capacitive sensing is one type of touch sensing technologies. Some capacitive sensing technologies may be based on self-capacitance (also referred to as “absolute capacitance”) sensing and/or mutual capacitance (also referred to as “transcapacitance”) sensing. The self-capacitance sensing involves obtaining a sensing signal dependent on the self-capacitance of a sense electrode provided in the touch panel while the mutual capacitance sensing involves obtaining a sensing signal dependent on the mutual capacitance between a sense electrode and a drive electrode. Capacitive touch sensing is disclosed in Japanese Patent Application Publication No. 2015-141556.
A liquid crystal display (“LCD”) panel incorporating electrodes used for touch sensing, which may include sense electrodes and/or drive electrodes, may effectively reduce the volume of the entire display device and may be suitable for application to mobile terminals.
A sensing signal obtained from a sense electrode may be influenced by the state of the LCD panel. For example, inversion drive, which is performed to avoid “burn-in” of the LCD panel, may influence the sensing signal obtained from a sense electrode. The inversion drive involves inverting drive voltages written into respective pixel circuits of the LCD panel, and this causes large changes in the potential distribution around each sense electrode. The changes in the potential distribution around a sense electrode may influence the sensing signal obtained from the sense electrode. The influence of the inversion drive on the sensing signal may appear as generation of an offset in the sensing signal and may cause deterioration in the SNR (signal-to-noise ratio) of the sensing signal.
Accordingly, there is a need for providing a touch sensing technology which reduces an influence of the state of the liquid crystal display panel on the sensing signal.